1. Field of the Invention
The present invention relates to an apparatus and method for quantum cryptography communication, and more particularly to an apparatus and method for quantum cryptography communication suitable when relative positions between a transmitter and a receiver that perform quantum cryptography communication such as mobile communication in satellites and the like change.
2. Description of the Related Art
In the quantum cryptography communication, a method of generating synchronization signals for loopback in a transmitter and a receiver and transmitting the synchronization signals is proposed for synchronization between the transmitter and the receiver (see Patent Document 1 and Patent Document 2).
In the quantum cryptography communication, a method of exchanging synchronization pulses between QKD stations and locking a phase is proposed in order to surely perform detection of a weak quantum signal (see Patent Document 3).
Further, in the quantum cryptography communication, a method of detecting an optical clock with a photodetector and inputting the output of the detection to a synthesizer via a narrow-band filter to generate timing is proposed (see Patent Document 4).
Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-260911;    Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-117512;    Patent Document 3: National Publication of International Patent Application No. 2006-513678; and    Patent Document 4: Japanese Laid-Open Patent Publication No. 2004-356996.